In an effort to reverse an "overwhelming increase" in heroin abuse in Ocean City this year, police in Maryland's largest beach resort launched a broad, weeks-long investigation into the local drug trade — resulting last week in the indictments of more than 20 people on felony drug charges.

The large bust — which has netted more than 100 bags of heroin — comes at a time when law enforcement agencies across the state have focused on prescription drug fraud and abuse, resulting in prescription addicts unable to obtain the drugs they are dependent on turning to the streets for their fix, said Officer Michael Levy, an Ocean City police spokesman.

"We, like everybody else — the medical community, the state of Maryland and our neighboring jurisdictions — are really cracking down on prescription fraud and prescription drug abuse, and what you're seeing is the prescription-addicted person now turning to the illegal opiates, heroin being the cheapest and easiest to get on the street," Levy said.

This year, Ocean City police have seen an increase of nearly 550 percent in heroin cases, compared with last year, Levy said.

That's on top of a general increase in the number of drug arrests in Ocean City during the past five years, according to police data. In 2007, there were 785 drug arrests. That number has increased every year since, and in 2011, there were 1,166 drug arrests.

"We're seeing a very dramatic increase in the presence of heroin in the community, so we've obviously had to make that a priority," he said. "It's really disturbing."

The sweeping investigation, called Operation Smackdown, in recent weeks involved more than 70 drug purchases by undercover officers of heroin, cocaine, marijuana and prescription drugs — though most involved heroin, police said.

Maryland State Police and the Worcester County sheriff's office cooperated in the operation, police said.

On Nov. 27, city narcotics officers took their investigation before a Worcester County grand jury, which indicted 23 men and women on drug distribution charges, police said. Most are from Ocean City and the nearby town of Berlin. Bonds set for those in custody varied between $100,000 and $300,000, police said.

Of those indicted, most of whom face felony charges, 17 are in police custody and six are being sought, police said.

The investigation has also led to multiple other arrests.

On Thursday, Ocean City detectives served a search warrant at the Ocean City home of Louis Joseph Rychwalski III, 27, where they found him in possession of four "bundles" of heroin, or 46 bags, police said. More heroin, drug paraphernalia and two replica guns were also found in the home, police said.

While at the home, police also arrested Nicholas Alexander Palmisano, 18, and Edward Allen Paddy, 37, both of Ocean City, after they arrived at Rychwalski's house, allegedly to purchase heroin, police said.

On the same day, officers attempting to locate indicted suspects stopped a car containing one of the suspects, Shelly Anne Brittingham, 41, of Delmar, Del., and recovered 63 bags of heroin, police said.

The stop also led to the arrests of Quamine Lamar Huggins, 20, of Delmar, and Stephanie Lynne Orick, 24, of Hebron, for possession of heroin with the intent to distribute, and the arrest of the driver, Markel Lamar Barkley, 21, of Quantico, on a possession charge.

Prosecutors announced new indictments Monday of Baltimore jail staff, the same day a top corrections official testified in the federal corruption trial of eight inmates and corrections officers about the difficulty containing misconduct in the system.